1. Field of the Invention
The present invention relates to a dipyrromethene metal complex compound and a tautomer thereof, a colored curable composition suitable for forming a color filter which is used in a liquid crystal display device or a solid-state imaging device, and a color filter using the colored curable composition and a method of producing the same.
2. Description of the Related Art
One method of producing a color filter used in a liquid crystal display device or a solid-state imaging device is a pigment dispersion method. There is a method of producing a color filter by photolithography using a colored radiation-sensitive composition obtained by dispersing a pigment in a variety of photosensitive compositions by the pigment dispersion method. Since a pigment is used in this method, the resultant composition is stable with respect to light and heat, and since patterning is performed by photolithography, sufficient positional precision can be ensured. Thus, this method has been widely utilized as a method suitable for producing a color filter for a large screen and a high-definition color display.
In preparing a color filter by the pigment dispersion method, the radiation-sensitive composition is first applied onto a substrate with a spin coater or roll coater and dried to form a coating film. Then, colored pixels are obtained by pattern exposure and development of the coating film. The color filter can be prepared by repeating this operation a number of times corresponding to the number of hues.
Recently, even higher resolution has become desirable in color filters for solid-state imaging devices; however, it is difficult to further improve the resolution with conventional pigment dispersions. Problems such as the generation of color irregularities due to coarse particles of the pigment result in a lack of suitability for uses which require fine patterns such as solid state image sensing devices.
Use of a dye as the colorant has been conventionally studied from the viewpoint of improvement in resolution above (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 6-75375). However, such dye-containing curing compositions have the following additional problems:
(1) Dyes generally have lower light stability and/or lower heat resistance than pigments.
(2) It is difficult to obtain a liquid curable composition having a desired spectrum with a common colorant, because such a colorant is less soluble in an aqueous alkaline solution or organic solvent (hereinafter, also simply referred to as a “solvent”).
(3) It is difficult to control the solubility (developing efficiency) of the cured area and the uncured area, because the dye used often interacts with other components in the curable composition.
(4) When the molar absorption coefficient (ε) of the dye used is low, a large amount of the dye should be added, and thus the amounts of the other components in the curable composition, such as polymerizable compound (monomer), binder, and photopolymerization initiator must be reduced, which leads to deterioration in the curing efficiency of the composition, the heat resistance after curing, and the developing efficiency of the cured area or uncured area.
Due to these problems, it has been difficult to form a thin film of fine colored patterns for high-definition color filters. Unlike those used in the production of semiconductors, it is necessary to use a thin film having a thickness of 1 μm or less for the production of color filters for solid-state imaging devices. It is thus necessary to add a larger amount of a colorant to the curable composition in order to obtain a desired absorption, leading to the problems described above.
Next, the conventional art with respect to a high fastness dye will be described. Generally, coloring agents which are used in a variety of applications are commonly required to have the following properties. That is, the coloring agents are required to have absorption properties which are preferable in terms of color reproducibility, fastness in use environment conditions (for example, good heat resistance, good light resistance and good humidity resistance), and large molar absorption coefficients, and are required to be easily formed into a thin film.
For example, a dipyrromethene metal complex is known to be used as a functional compound in a variety of applications, and is used as a sensitizer for a radical polymerization initiator in a visible photopolymerization composition (see, for example, Japanese Patent Nos. 3279035 and 3324279, and JP-A Nos. 11-352685, 11-352686, 2000-19729, 2000-19738, and 2002-236360). In addition, the dipyrromethene metal complex is known to have a high molar absorption coefficient, and have absorption properties which are preferable in terms of color reproducibility (see, for example, US Patent Application Publication No. 2008/0076044 A1).
On the other hand, particularly in a color filter of a solid-state imaging device, fine pattern forming properties are required, and it is difficult to regulate solubility (developability) of a cured area and a uncured area. Specifically, a fine pattern is formed by light exposure through a mask having a fine pattern, and subsequent development with an alkaline liquid to dissolve an unexposed area in an alkali developer. However, when the solubility of a colored curable composition in an alkali developer is poor, pattern forming properties are deteriorated (i.e., a colored material remains at an unexposed area). Accordingly, a colored curable composition having low dependency on the concentration of the alkali liquid is sought.